Containers for beverages such as milk and juices are conventionally constructed from thermoplastic coated paperboard. One common type of these containers includes a top end closure with a folded gable roof having a vertically projecting sealed fin at the roof ridge for sealing the container. Such containers are shown by U.S. Pat. No. 3,270,940. The bottom end closure for same is conventionally of the infolded type, such as that shown by U.S. Pat. No. 3,120,335.
Another type of container includes a slant top or a flat top end closure wherein what could otherwise be a vertically projecting sealed fin, or a slanted sealed fin, may be folded flat and releasably secured to the rest of the closure. U.S. Pat. Nos. 3,869,078 and 4,211,357 disclose such slant and/or flat top closures.
Various techniques have been employed to enhance the folding of a sealed fin in one particular direction to facilitate packing the containers in layers on top of each other to minimize storage and cargo space, without requiring any shipping tray between layers. For example, in U.S. Pat. No. 4,078,715 there is disclosed a top end closure with an inclined sealed fin that includes a "harder crease" on one side thereof than on the other for facilitating folding of the sealed fin from a vertical position to the inclined position.
U.S. Pat. Nos. 4,012,997 and 4,093,115 disclose a container folding method and the container made by the method, wherein one side of the gable panels of the top end closure is provided with double score lines extending parallel to each other. Folding of a sealed top fin of the end closure from a vertical position to a flat position requires the application of a downward force against the outside panel to bend the sealed fin downwardly.
In U.S. Pat. No. 4,206,867, a wide score line is formed on one side of the gable panels, in lieu of the above mentioned double score lines, with a conventional score line of the opposite side providing unequal fold-back panels.
In the above-mentioned U.S. Pat. No. 4,211,357, unequal angles at the base of the infolded gable or gusset panels, with or without lower score lines on one side thereof than on the other, enhance folding in the direction of the larger base angles. In an alternative embodiment, a lowered and/or inclined wide score line provide the inclination to slant in one direction.
U S. Pat. No. 4,422,570 is an example of an improved flat top end closure for a liquid carrying, paperboard container wherein the sealed fin previously used in conjunction with flat end closures is not required, but wherein a pitcher pour spout is included. An external lift tab is integrally formed on one outer closure panel for initial lifting of a portion of the pitcher pour spout, and an underlying lift tab is formed on one fold-back closure panel of another portion of the pitcher pout spout, in order to facilitate the opening process.
In liquid carrying paperboard container constructions generally, for sensitive food products, such as milk or fruit juice, it is essential that the top closure be thoroughly sealable so as to be clean and sanitary and yet be functional from the standpoint of including means for readily opening the pouring spout thereof. As illustrated and described in the above-mentioned U.S. Pat. No. 3,270,940, anti-adhesive or "abhesive" patterns have been utilized, primarily on one or both sides of the rib panels located outward of the infolded triangular fold-back panels and inward of the outer edge sealing flaps. In the flat top structure disclosed in the above-mentioned U.S. Pat. No. 4,422,570, wherein there is no conventional sealing fin, such as the usual rib panels and sealing flaps, other arrangements for releasably sealing the top closure are required.
U.S. Pat. No. 4,582,246 discloses a flat top closure of the non-sealing fin type disclosed in the above-mentioned U.S. Pat. No. 4,422,570, and including predetermined inner and outer surface adhesive patterns, and an optional embossment filled with a supplementary sealant material, and/or partial cut lines which serve to facilitate the container opening operation.